Electronic inductor

Abstract

To produce a high current carring inductor with a high inductance value in space normally too small, a transformer is chosen which meets space requirements and has a primary winding of sufficient current capacity, but too little inductance. A bidirectional current source drives the secondary winding under control of a feedback circuit in response to sensed primary winding current to effectively multiply the primary winding inductance.

I claim: 
     
       1. An electronic inductor comprising: an inductance transformer (20) having a primary inductance winding (18) and a secondary inductance winding (19);   current sensing means (16) for sensing the current in the primary inductance winding;   a bidirectional current source (20) connected to said secondary inductance winding; and   control means (41) reponsive to said current sensing means and connected to said bidirectional current source for controlling the current in said secondary inductance winding to substantially increase the inductance effect of said primary inductance winding.   
     
     
       2. An electronic inductor, as in claim 1, wherein said inductance transformer has a magnetic core. 
     
     
       3. An electronic inductor, as in claim 2, wherein said current sensing means comprises a current sensing transformer having a primary sensing winding connected in series with said primary inductance winding and a secondary sensing winding. 
     
     
       4. An electronic inductor, as in claim 2, wherein said bidirectional current source comprises: an operational amplifier (31) having an inverting input (32), a non-inverting input (33) and an output;   output resistance means (34) connected between said operational amplifier output and said secondary inductance winding;   a first feedback resistance (35) connected between said output and said inverting input;   a second feedback resistance (36) connected between said secondary inductance means and said non-inverting input;   a first input resistance (38) connected between said control means and said inverting input; and   second input resistance (37) connected between said non-inverting input and circuit ground; and   wherein the ratio of said first feedback resistance to said first input resistance is substantially equal to that of said second feedback resistance to said second input resistance.   
     
     
       5. An electronic inductor, as in claim 2, wherein the primary to secondary turns ratio of said inductance transformer is less than 10. 
     
     
       6. An electronic inductor, as in claim 4, wherein the primary to secondary turns ratio of said inductance transformer is less than 10.